Automotive Suppliers: Quality Control

An automotive industry supplier produces pistons for several models of automobiles. Twenty samples, each consisting of 200 pistons, were selected when the process was known to be operating correctly. The numbers of defective pistons found in the samples follow.

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a.What is an estimate of the proportion defective for the piston manufacturing process when it is in control?
b.Construct the p chart for for the manufacturing process, assuming each sample has 200 pistons.
c.With the results of part (b), what conclusion should be made if a sample of 200 has 20 defective pistons?
d.Compute the upper and lower control limits for an np chart.
e.Answer part ( c ) using the results of part ( d ).